It is of course well established that transverse or bluff surfaces on vehicles traveling down a highway provide considerable wind resistance in the form of aerodynamic drag. In particular, the flat bluff surface at the front or windward side of a trailer in a tractor-trailer unit provides considerable area exposed to aerodynamic forces occasioned by the travel of the vehicle on a highway at typical speeds in the range of fifty to sixty miles per hour, it being well known that such drag forces increase as the square of the speed. Typically, decreased efficiency of twenty percent or more occurs, and fuel use and cost, in turn, is increased a significant amount.
Recently, when fuel costs have themselves increased by substantial amounts, this problem has received considerable attention and attempts have been made to decrease the aerodynamic drag to reduce fuel costs and provide generally higher efficiency in the operation for a given cargo load. While it is known that generally curving the corners adjacent the bluff forward surface of a trailer will reduce the aerodynamic drag, a dilemma occurs since such curving of corner edges reduces cargo capacity. As a consequence, specific attempts have been made to provide attachments for the existing maximum cargo, generally rectangular boxlike configurations of the trailer so that the same may be retained yet enable reduction of aerodynamic drag and the attendant inefficiency of operation. However, such attempts have been in general but partially effective, due primarily to a limited understanding of aerodynamic forces.